<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>左侧占30%宽度，右侧占70%宽度</title>
<style>
    body{
        width: 100%;
        margin: 0px;
    }
.box1{
    width: 30%;
    height: 400px;
    background-color: darkkhaki;
    float: left;
}
.box2{
    width: 70%;
    height: 400px;
    background-color: darkcyan;
    float: left;
}
</style>
</head>
<body>
    <div class="box1">111</div>
    <div class="box2">222</div>
   
</body>
</html>